The present invention relates to apparatus for delivering flashes of light to the eyes, and to methods of using the apparatus. The invention has particular, but not exclusive, application to the treatment and prevention of migraine, pre-menstrual syndrome, insomnia and nervous tension. Attention is directed to the applicant's publication "The Treatment of Migraine with Variable Frequency Photo-Stimulation" D. J. Anderson, Headache, Mar. 1989, pages 154 and 155, which is incorporated herein by reference.
The following definition of migraine has been given in J. N. Blau "Towards a Definition of Migraine Headache", Lancet, 1984, 1, pages 444 to 445. "Episodic headache lasting from 2 to 72 hours with total freedom between attacks. The headaches must be associated with visual or gastrointestinal disturbance or both. The visual symptoms occur as an aura before and/or photophobia during the headache phase. If there are no visual but alimentary disturbances, then vomiting must feature in some attacks." An alternative definition is given in "Classification of headache disorders, cranial neuralgias and facial pain; and diagnostic criteria for primary headaches disorders" available from the International Headache Society and abbreviated from Cephalalgia 1988; 8 suppl. 7:1-69, which is incorporated herein by reference.
Pre-menstrual syndrome has been defined as "the cyclic occurrence of symptoms that are of sufficient severity to interfere with some aspects of life and which appear with consistent and predictable relationship to menses" in Endicott J., Halbreich U., Schacht S. and Nee J. "Premenstrual changes and affective disorders" Journal of Psychosomatic Medicine 1981, Vol. 43, page 519, and quoted in "The Premenstrual Syndromes" ed. L. H. Gise, published 1988 by Churchill Livingstone, New York, Edinburgh, London, Melbourne.
Insomnia has been defined as consisting of "difficulty in initiating or maintaining sleep at least three times a week for at least a month. The loss of sleep produces significant day time fatigue or impaired occupational or social functioning. In typical cases, sleep latency exceeds 30 minutes or sleep efficiency is less than 85%", in "Phychiatric Dictionary" 6th edition, ed. R. J. Campbell 1989, Oxford University Press. Further details may be found in "Diagnostic and Statistical Manual of Mental Disorders" 3rd edition, Revised 1987, which is often referred to as "DSM-111-R". Further information is also available in "Oxford Textbook of Psychiatry", ed. Michael Gelder, 1989, Oxford University Press, especially at pages 399 and 400.
Nervous tension or stress is a psychological state with physiological consequences including increased muscle tension and an inability to relax, and is often accompanied by difficulty in concentrating and difficulty in sleeping.
All of these conditions are distressing or unpleasant for their sufferers. Although some advances have been made in understanding the causes of these conditions, there remains a need for curative and/or preventative treatments which are cheap, simple and effective.
It has been suggested by G. D. Solomon "Slow wave photic stimulation in the treatment of headache--a preliminary study", Headache 1985, 25, pages 444 to 446, that the use of light at a frequency range of 1 to 3 Hz for 5 minutes provided relief for muscle contraction headaches but not for migraine. The enhancement of brain alphawaves by bio-feedback has been used in the treatment of people with migraine, and according to M. J. Cohen, D. L. McCarthar and W. H. Rickles "Comparison of four bio-feedback treatments for migraine headaches: physiological and headache variables", Psychosomatic Medicine, 1980, 42, pages 463 to 480, this reduced the number of migraine headaches per week but did not change intensity, duration or disability of the headaches. It has been suggested, by D. Lewis "The alpha plan", published by Methuen in London in 1986, at page 26, that red stroboscopic light tends to produce rapid and powerful alpha brain rhythms in the occipital cortex. These prior art publications do not lead to any clear or definite conclusion about either the causes or the treatment of migraine, and at present treatments are typically based on the control of diet and the use of drugs.
Pre-menstrual syndrome is generally considered to be caused by hormonal changes during the menstrual cycle, and is generally treated using drugs.
Insomnia and nervous tension or stress are generally treated psychologically or with drugs, especially the major and minor tranquilisers.
British Patent 2,196,442, of the present applicant, proposes a device for flashing light into the eyes of a user, either alternately or synchronously. It is suggested that the light should be provided by light sources mounted in the eyepieces of goggles. No disclosure is given of the frequency of the flashes. There is no suggestion that the goggles should be in any way darkened or obscured so as to reduce the ambient light also reaching the eyes of a user. There is no suggestion of any purpose or beneficial effect of use of the device.